Land grid array (LGA) interposers, by way of example, provide an array of interconnections between a printed wiring board (PWB) and a chip module, such as a multichip module (MCM), among other kinds of electrical or electronic devices. LGA interposers allow connections to be made in a way which is reversible and do not require soldering as, for instance, with ball grid arrays or column grid arrays. Ball grid arrays are deemed to be somewhat unreliable on larger areas because the lateral thermal coefficients of expansion-driven stresses that develop can exceed the ball grid array strength. Column grid arrays hold together despite the stresses, but are still soldered solutions, and thus, do not allow for field replaceability, which can be significant since replaceability could potentially save a customer costs in the maintenance and upgrading of high-end computers for which LGAs are typically used.
Various types of LGA interposer structures have been developed, but generally include, for instance, rigid, semi-rigid, or flexible substrate structures having arrays of electrical contacts formed by, for example, spring structures, metal-elastomer composites, wadded wire, etc. State of the art LGA techniques enable MCM-to-board interconnections with I/O interconnect densities/counts and electrical/mechanical properties that are desirable for high-performance CPU module designs. Moreover, LGA provides electrical and mechanical interconnect techniques that allow MCM chip modules to be readily removable from wiring or circuit boards, which is advantageous for high-end modules such as CPU packages which may require repeated re-work during production or are designed to be field-upgradable.